Long addition for integers
-9 + 6 + (-7) +3=-9 +6 = -3-3 + (-7)= -10-10 +3= -7
-4 + 9 = 5
-81 + -56 = -137
40 + 23 = 63
positive + negative (convert it to subtraction the sign changes when it depends on the higher number)
negative + negative = negative
positive + positive = positive
